Drugs administered either orally or intravenously bind specific receptors in order to produce expected pharmacologic actions. However, the drugs may also bind to plasma proteins in the circulation. This binding affects the distribution and half-life of the drugs and causes undesirable side effects. The amount of a drug that is free from binding by the proteins is critical for pharmacological action. Ultrafiltration and equilibrium dialysis can be used to determine the concentration of the unbound fraction of the total administered drug.
Conventional equilibrium dialysis requires incubation times as long as 6 to 16 hours to reach a steady state equilibrium. This long incubation time may associate with a volume shift from the dialysate to the plasma-containing solution due to osmotic pressure differences. This shifting can result in plasma protein dilution and has been shown to reduce the in vitro fractional binding of a compound to plasma proteins. Also, the long incubation time may affect the stability of the compound.
Thus, there is a need for an efficient and accurate method and device for the equilibrium dialysis.